Each kit will give you 120 tests.

  1. Using the 5 ml syringe add 5ml of aquarium water to the test vial.
  2. Using the 1 ml syringe, place the metal needle firmly and draw up the KH solution until the lower end of syringe's black rubber is right on the 1.00 ml mark.
    • Before this step, ensure that the metal needle is empty of liquids and that it's submersed in water the entire time to avoid air entering to the syringe.
    • The presence of small layer of air between the liquid and the black part of syringe is normal and will not affect the result (The normal air layer you should see is equal to 0.01 ml).
  3. Start adding KH solution to the test vial one drop at a time, swirling a little after each drop. After 2-3 drops you will get solution with blue color       
  4. Continue adding KH solution to the test vial until the color will change to yellow       
    • There will be short stage of green color. The final result is when the solution is changed from green color to yellow. When the solution is green you are very close to the final result - about (1-2 drops).
    Pay attention that by adding KH solution more than needed the yellow color will get brighter. ­­­ 5.
  5. Note the position of the lower black part of syringe (each division corresponds to 0.01 ml) and obtain the KH result from the table. Readings should be taken at the position of the lower end of syringe's black rubber.


  • Testing tap water or freshwater aquariums for General Hardness (GH) and Carbonate Hardness (KH). Helps detect stress on fish caused by unwanted or uncontrolled pH changes, which result from low KH levels and helps hobbyists stay as close as possible to the natural habitat of their fish. Some tap water supplies have a very low KH level (below 3 °dKH). This type of water has very little pH buffering capacity and can contribute to wide pH swings in the aquarium.

    KH- Carbonate Hardness known as alkalinity, is the measure of Carbonate and Bicarbonate ions concentrations dissolved in water. Carbonate Hardness helps stabilize pH in the aquarium. An aquarium with a low KH level (50 ppm or less) will tend to be acidic. Aquariums with very low KH are subject to unwanted or uncontrolled pH changes, if not monitored carefully. Water with a high KH level (= 200 ppm) usually has a high ph. The Royal KH professional test measures KH in (°dKH) and contains 120 tests. To convert °dKH to ppm, multiply °dKH x 17.9. It is therefore necessary to test the GH and KH frequently to monitor water quality and prevent stressful conditions.

    GH & KH RANGE – recommended values.

    0°-3° dKH ( 0-50 ppm) discus, arowanas, elephant nose, neons, cardinals, live plants
    3°-6°  Dkh (50-100 ppm) Most tropical fish including angelfish, cichlids, tetras, botia, live plants
    6°-11° Dkh (100-200 ppm) Most tropical fish including swordtails, guppies, mollies, goldfish
    11°-22° dKH (200-400 ppm) Rift lake cichlids, goldfish, brackish water fish